The present invention is directed to the disposal of scrap or used rubber products, and more specifically to reinforced rubber products such as automobile and truck tires, conveyor belts and the like and still more particularly to a method and apparatus utilizing ozone (O.sub.3) to destroy or disintegrate the rubber and rubber products and separate the rubber from the reinforcement materials.
The disposal of various used or spent rubber products, especially reinforced rubber products such as tires, conveyor belts, and the like, has long been recognized as a major environmental problem. The recycling of solid waste materials, particularly reclaimable, useful materials, such as tires from automobiles, trucks and tractors and such is of great importance from the standpoint of conservation of resources as well as pollution abatement.
It has been estimated that over 280 million spent rubber tires are discarded every year in the United States and over two billion scrap tires litter the landscape, dumped in land-fills or oceans off-shore. Most of the discarded tires are located in open dumps where they collect rain or run-off water and serve as fertile breeding grounds for mosquitoes, rats and other pests.
In earlier years, these scrap tires were burnt in open pits or furnaces causing enormous air pollution problems in terms of the noxious gases produced during combustion. A common disposal method currently in use is burying them in land-fills but this method has its own attendant problems in that it fills up valuable space fast and more additional sites need to be found. Furthermore, the tires when buried whole under eight feet or so of soil or solid waste, refuse to stay buried and float to the top. Another method for the disposal of spent tires consists of cutting up or shredding the tires prior to dumping them in land-fills. However, cutting equipment to dispose of the tires efficiently is costly and requires frequent replacement or repairing of the cutting tools or surfaces, especially if the tires are reinforced with steel wires and fiber mesh. More recently, scrap tires are being considered as a source of fuel and are being used in large incinerators to extract energy therefrom. See M. W. Mayo et al., "Processing Scrap Tires For Multiple Markets," Solid Waste & Power, March/April, 1992.
In recent times, automotive tires have been reinforced with fiber and steel or other metal belts or cords for greater durability and stability. With the advent of fabric and metal reinforcement of tires, and the reduction of the tire recapping industry because of the difficulty in recapping reinforced tires, the presence of steel and other materials poses additional difficulties in the disposal of these materials. Efforts have been directed to removing the reinforcement materials from the rubber prior to disposal but the disposal of the reinforcement material in and of itself poses an additional pollution problem.
Methods of alleviating some of these disposal problems include using tire sections for decorative purposes, cutting of the rubber from the reinforcement materials, shredding the tires, cooling the tire pieces to the brittling temperature of rubber and pulverizing the rubber using sledge or drop hammers. The pulverized rubber is then used for various purposes such as asphalt paving, soles for shoes, to line land-fills and the like.
These prior art methods for the disposal and/or recycling of scrap or discarded tires are exemplified by U.S. Pat. Nos. 4,142,688 issued Mar. 6, 1979; 4,180,004 issued Dec. 25, 1979 to A. O. Johnson; 4,726,530 issued Feb. 23, 1988 to D. Miller et al; 4,757,949 issued Jul. 19, 1988 to N. P. Horton; 4,839,151 issued Jun. 13, 1989 to F. Apffel; 4,840,316 issued Jun. 20, 1989 to R. L. Barclay; 5,057,189 issued Oct. 15, 1991 to F. Apffel; 5,097,905 issued Mar. 10, 1992 to K. N. Murray; and 5,115,983 issued May 26, 1992 to D. Rutherford, Sr. In addition, efforts were also being made in other countries to address the pollution problem caused by scrap tires. These efforts are exemplified by U.S.S.R. Author Certificates Nos. 1685721 dated 05.06.89 and 1698075 dated 12.02.90; and British Patent Specification No. 1438278 by J. R. Lanning, published Jun. 3, 1976.
While these prior art approaches have served to reduce the volume of discarded tires and tire materials, the energy efficiency, cost-effectiveness and environmental efficacy of these prior efforts leave a great deal to be desired. Consideration must also be given to the capability of such approaches being readily portable for in situ applications, as well as the capability to be easily scaled up for large production-type facilities. While the prior systems may be environmentally acceptable that they may be located at sites remote from residential areas, they are not energy-efficient or cost effective in that the discarded tires need to be transported to the remote location. The processes involved are also energy-intensive which is a disadvantage in these times of a need for energy conservation. Some methods for tire disposal or treatment such as the recovery process disclosed in the Apffel patent '151 involves the pyrolysis of the tire consumes enormous amounts of energy. Similarly, the cold crushing method described by Lanning (Br. Pat. '278) requires the deep cooling of the tire, using liquid nitrogen, to its brittling temperature. Methods requiring either heating and cooling consume significant amounts of energy and make the operation prohibitively expensive. Therefore, there is a need in the art for a technique by which reinforced rubber products, such as tires, can be recycled, and which is energy-efficient, cost-effective and responsive to environmental concerns.
It has long been recognized that rubber is subject to oxygen and ozone degradation. In the manufacture of tires, for example, substantial efforts have been directed to eliminating or reducing ozone degradation by the addition of anti-oxidants to rubber formulations. These efforts are exemplified by U.S. Pat. Nos. 5,023,227 issued Jun. 11, 1991 to L. R. Evans et al; 5,025,066 issued Jun. 18, 1991 to J. L. De Rudder et al; 5,088,537 issued Feb. 18, 1992 to M. Kan; and 5,120,844 issued Jun. 9, 1992 to E. L. Wheeler et al. The time required for tire degradation with the ozone content in the atmosphere is much too long (more than one year) to be utilized for practical purposes. Even when the ozone concentrations are increased to environmentally acceptable levels, the degradation times of more than one week are still too long for practical applications. (Natural Rubber Science and Technology," Ed. A. D. Roberts, Oxford University Press, 1988). It has also been known that the relationship of the rate of rubber degradation to the ozone concentration is not linear even at low ozone concentration levels, especially in the presence of antioxidants. Beyond a certain threshold level of ozone concentration, the effect of the antioxidant is also suppressed, making this nonlinear relationship even more complex. For certain antioxidants, this threshold level is near 0.1% ozone. (M. Braden & A. N. Gent, J. Appl. Poly. Sci., 6, 449(1962).
Thus, while it has been widely recognized that the effects of ozone on tires needed to be addressed in the manufacture of tires, it has not been previously appreciated that this same tire degrading environment can be effective in the decomposition of tires for recycling purposes. It would be desirable, therefore, to have a method for the disposal of reinforced tires which does not require burning, cooling or shredding of the tire.
It is an object of the present invention, therefore, to provide a technique for the disposal of used or spent reinforced or unreinforced rubber products which is energy-efficient, cost-effective and environmentally responsible.
A further object of the invention is to provide a method for recycling reinforced rubber products.
Another object of the invention is to provide a readily portable apparatus for in situ disposal of used or spent reinforced rubber products.
Yet another object of the invention is to provide a method and apparatus for removing steel mesh or belts from steel-belted tires without destruction of the steel mesh or strands.
A further object of the invention is to provide a method and apparatus for the disposal of reinforced rubber products without significant heating or cooling of the rubber product.
A further object of the invention is to provide a method and apparatus for the disposal of used or spent reinforced or unreinforced rubber tires by placing the tires in an ozone atmosphere, either at room temperature or at lower or higher temperatures, and in a strained state causing rapid breakdown of the rubber.
Another object of the invention is to provide a method and apparatus for disposing of reinforced rubber tires which can be readily adapted for individual or continuous operation and can accommodate different tire sizes.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows and the drawings incorporated hereinto, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.